A high-powered ultrasound beam can destroy prostate cancer without causing the serious side effects that plague other treatments, a London study found.

Trials in London and Basingstoke, southeastern England, found it was possible to obliterate tumor cells without damaging delicate surrounding tissues.

Conventional surgery or radiotherapy for prostate cancer leaves half of men impotent and a fifth incontinent. The side effects are so common that many men with slow-growing tumors are advised not to have treatment.

Doctors used an experimental procedure High Intensity Focused Ultrasound (HIFU) to destroy tumors during the trial.

None of the 41 men treated had incontinence and only 10 percent had impotence, the Lancet Oncology journal reported.

Dr. Hashim Ahmed, of University College London Hospital, said, "We're optimistic that men diagnosed with prostate cancer may soon be able to undergo a day-case surgical procedure, which can be safely repeated once or twice, to treat their condition with very few side effects. That could mean a significant improvement in their quality of life."

The doctors used high-resolution MRI scans of the men's prostates to map the precise location of the tumors. They then used HIFU machines to focus ultrasound waves onto an area the size of a grain of rice.